perf(mangler): store slot indexes as u32s

[overlookmotel]

There cannot be more slots than symbols, and SymbolId is a u32, so there can't be more than u32::MAX symbols. Therefore we can store slot indexes as u32 too.

[overlookmotel]

• perf(mangler): store slot indexes as u32s #13462 👈 (View in Graphite)
• perf(mangler): do not sort Vec if empty #13461
• main

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[Boshen]

Merge activity

• Aug 31, 10:25 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Aug 31, 10:28 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Aug 31, 10:31 AM UTC: The Graphite merge queue couldn't merge this PR because it was in draft mode.
• Aug 31, 10:32 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Aug 31, 10:32 AM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Aug 31, 10:38 AM UTC: Merged by the Graphite merge queue.

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13462 will improve performances by 6.46%

_{Comparing 08-31-perf_mangler_store_slot_indexes_as_u32_s (0d66399) with main (caf40c5)¹}

Summary

⚡ 3 improvements
✅ 34 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	mangler[binder.ts]	780.8 µs	733.4 µs	+6.46%
⚡	mangler[cal.com.tsx]	2.9 ms	2.8 ms	+3.65%
⚡	mangler[react.development.js]	272.3 µs	259.5 µs	+4.96%

Footnotes

1. No successful run was found on main (0d66399) during the generation of this report, so caf40c5 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull Request Overview

This PR optimizes the mangler's slot storage by changing the slot index type from usize to u32. The optimization is based on the fact that there cannot be more slots than symbols, and since SymbolId is already a u32, the slot indexes can safely use the same type without risk of overflow.

Key changes:

• Changed Slot type alias from usize to u32
• Added explicit type casts with clippy suppressions where needed
• Moved sort_unstable() call to after empty check for minor optimization

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